Field of the Invention
The invention lies in the field of electronic signal transmission. The invention relates to a signal transmission unit and a method for transmitting an information item, in particular for an anti-theft protection system of a motor vehicle.
A known transmission unit (German Patent DE 195 42 441 A1) has at least one pair of coils disposed close together. A common control unit for the transmission of signals controls the two coils. The control unit is disposed close to the coils and between the two coils. Because vehicle-specific data are to be transmitted, a central controller feeds the vehicle-specific data to each respective control unit.
The vehicle-specific data are passed in binary form as square-wave signals through the wiring harness to the individual control units. The square-wave signals can have an interfering effect on other electrical equipment. This is because the square-wave signals have high-frequency harmonics with a non-negligible amplitude. The process of transmitting the vehicle-specific data can give rise to enormous EMC problems in the motor vehicle. In the known transmission unit, moreover, each coil pair requires its own separate control unit. If this was not the case, square-wave signals having even larger amplitudes would have to be passed to the coils so that a sufficiently large field with an adequate range could be generated. Accordingly, this would cause greater interference.
It is accordingly an object of the invention to provide a transmission unit and method for transmitting an information item, in particular for an anti-theft protection system of a motor vehicle, which overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and which is constructed in a simple manner and does not interfere with other electrical equipment, or does so only to a small extent.
The transmission unit of the invention has a generator that generates a sinusoidal carrier oscillation. A binary information item (corresponding to the vehicle-specific data) is modulated onto the carrier oscillation. A central transformer transforms the modulated oscillation from its primary side to its secondary side. In this case, the modulated oscillation is altered with regard to its amplitude. A plurality of antennas is connected to the secondary side, feeding the modulated oscillation to the antennas. The antennas generate an alternating field through which the vehicle-specific data are transmitted in modulated fashion.
With the foregoing and other objects in view, there is provided, in accordance with the invention, a transmission unit, having a generator for generating a sinusoidal carrier oscillation; a modulator for modulating an information item to be transmitted onto the carrier oscillation into a modulated oscillation; a transformer having a primary side and a secondary side for transforming the modulated oscillation from the primary side to the secondary side; and a plurality of antennas connected to the secondary side by which a respective electromagnetic field is generated for aiding transmission of the information item.
With the transmission unit, the antennas are fed only sinusoidal signals that have no harmonics or only harmonics with small amplitude. Therefore, the signals can be adapted in terms of their power to the antennas and an electromagnetic field generated by the signals can be adapted in terms of its range, without interference signals proceeding from the signals due to the data transmission to the antennas.
The transformer makes it possible for a plurality of antennas to be electrically disposed in parallel with the transformer. Therefore, the transformer can operate a plurality of antennas simultaneously. It is sufficient that the generator is a simple sine-wave oscillator generating the sinusoidal carrier oscillation. If the transformer is a step-up transformer, then the modulated oscillation is stepped up with regard to voltage and current, resulting in the generator generating a carrier oscillation with relatively small amplitudes. It is advantageous for the antennas to be constructed as coils, which are simple to produce and to mount at the fitting location.
In order to minimize the losses between the transformer and antennas, twisted two-wire lines are used. It is likewise possible to use two-pole, shielded lines, from which little interference radiation proceeds.
In accordance with another feature of the invention, the plurality of antennas are connected in parallel to the secondary side.
In accordance with a further feature of the invention, the generator is a sine-wave oscillator.
In accordance with an added feature of the invention, the transformer is a step-up transformer that steps up the modulated oscillation with regard to voltage and current.
In accordance with an additional feature of the invention, the plurality of antennas are coils in parallel with the secondary side and electrically connected to the secondary side.
In accordance with yet another feature of the invention, there is provided twisted two-wire lines, the plurality of antennas being electrically connected to the secondary side through the twisted two-wire lines.
In accordance with yet a further feature of the invention, there is provided a two-pole, shielded line, the plurality of antennas being electrically connected to the secondary side through the two-pole, shielded line.
With the objects of the invention in view, there is also provided a transmission unit of an anti-theft protection system of a motor vehicle, having a generator for generating a sinusoidal carrier oscillation; a modulator for modulating an information item to be transmitted onto the carrier oscillation into a modulated oscillation; a transformer having a primary side and a secondary side for transforming the modulated oscillation from the primary side to the secondary side; and a plurality of antennas connected to the secondary side by which a respective electromagnetic field is generated for aiding transmission of the information item.
With the objects of the invention in view, there is further provided a method for transmitting an information item, including the steps of providing a generator having a primary side and a secondary side, a modulator, a transformer, and a plurality of antennas; connecting the plurality of antennas to the secondary side of the transformer; creating an information item to be transmitted; generating a sinusoidal carrier oscillation; modulating the information item onto the carrier oscillation and forming a modulated oscillation; transforming the modulated oscillation from the primary side to the secondary side; and generating an electromagnetic field by the plurality of antennas to aid transmission of the information item.
In accordance with another mode of the invention, there is provided the step of connecting the plurality of antennas in parallel to the secondary side.
In accordance with a further mode of the invention, the step of providing the generator includes providing a sine-wave oscillator as the generator.
In accordance with an added mode of the invention, the step of providing the transformer includes providing a step-up transformer, and stepping up the modulated oscillation with regard to voltage and current with the step-up transformer.
In accordance with an additional mode of the invention, the step of providing the plurality of antennas includes providing coils, and electrically connecting the coils in parallel with the secondary side.
In accordance with yet another mode of the invention, there is provided the steps of providing twisted two-wire lines and electrically connecting the plurality of antennas to the secondary side through the twisted two-wire lines.
In accordance with yet a further mode of the invention, there is provided the step of providing a two-pole, shielded line, and electrically connecting the plurality of antennas to the secondary side through the two-pole, shielded line.
In accordance with a concomitant mode of the invention, there is provided a method for transmitting an information item in an anti-theft protection system of a motor vehicle, including the steps of providing a generator having a primary side and a secondary side, a modulator, a transformer, and a plurality of antennas; connecting the plurality of antennas to the secondary side of the transformer; creating an information item to be transmitted; generating a sinusoidal carrier oscillation; modulating the information item onto the carrier oscillation and forming a modulated oscillation; transforming the modulated oscillation from the primary side to the secondary side; and generating an electromagnetic field by the plurality of antennas to aid transmission of the information item.
Other features that are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a transmission unit and a method for transmitting an information item, in particular for an anti-theft protection system of a motor vehicle, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.